The frequency and infrared brightness of circumstellar discs at white dwarfs

White dwarfs whose atmospheres are polluted by terrestrial-like planetary debris have become a powerful and unique tool to study evolved planetary systems. This paper presents results for an unbiased Spitzer IRAC search for circumstellar dust orbiting a homogeneous and well-defined sample of 134 single white dwarfs. The stars were selected without regard to atmospheric metal content but were chosen to have 1) hydrogen rich atmospheres, 2) 17 000 K < T_eff < 25 000 K and correspondingly young post main-sequence ages of 15-270Myr, and 3) sufficient far-ultraviolet brightness for a corresponding Hubble Space Telescope COS Snapshot. Five white dwarfs were found to host an infrared bright dust disc, three previously known, and two reported here for the first time, yielding a nominal 3.7% of white dwarfs in this post-main sequence age range with detectable circumstellar dust. Remarkably, complementary HST observations indicate that a fraction of 27% show metals in their photosphere that can only be explained with ongoing accretion from circumstellar material, indicating that nearly 90% of discs escape detection in the infrared, likely due to small emitting surface area. This paper also presents the distribution of disc fractional luminosity as a function of cooling age for all known dusty white dwarfs, suggesting possible disc evolution scenarios and indicating an undetected population of circumstellar discs.Comment: 17 pages, 5 figures and 4 tables. Accepted for publication in MNRA

Uniqueness and Non-uniqueness in the Einstein Constraints

The conformal thin sandwich (CTS) equations are a set of four of the Einstein equations, which generalize the Laplace-Poisson equation of Newton's theory. We examine numerically solutions of the CTS equations describing perturbed Minkowski space, and find only one solution. However, we find {\em two} distinct solutions, one even containing a black hole, when the lapse is determined by a fifth elliptic equation through specification of the mean curvature. While the relationship of the two systems and their solutions is a fundamental property of general relativity, this fairly simple example of an elliptic system with non-unique solutions is also of broader interest.Comment: 4 pages, 4 figures; abstract and introduction rewritte

Inhibition of protein crystallization by evolutionary negative design

In this perspective we address the question: why are proteins seemingly so hard to crystallize? We suggest that this is because of evolutionary negative design, i.e. proteins have evolved not to crystallize, because crystallization, as with any type of protein aggregation, compromises the viability of the cell. There is much evidence in the literature that supports this hypothesis, including the effect of mutations on the crystallizability of a protein, the correlations found in the properties of crystal contacts in bioinformatics databases, and the positive use of protein crystallization by bacteria and viruses.Comment: 5 page

Synthesis and evaluation of β-substituted fosmidomycin analogues as inhibitors of 1-deoxy-D-xylulose 5-phosphate reductoisomerase

Blocking the MEP pathway for isoprenoid biosynthesis offers interesting prospects for inhibiting Plasmodia growth. Fosmidomycin (1) and its homologue FR900098 (2) potently inhibit 1-deoxy-D-xylulose-5-phosphate reductoisomerase (Dxr), a key enzyme in this pathway. Although fosmidomycin is a remarkably safe antimalarial agent, low oral absorption, short serum half-life and malaria recrudescence preclude its use in monotherapy. The development of more lipophilic Dxr inhibitors able to passively permeate into cells with improved pharmacokinetic properties could lead to more efficacious agents. Previously, we discovered that analogue 4, featuring a 3,4-dichlorophenyl substituent in α-position of the phosphonate, surpasses fosmidomycin’s potency in inhibiting P. falciparum growth. Here we explored the introduction of aryl or aralkyl substituents at the β-position of the known hydroxamate analogue 3. We studied the effect of introducing substituents in β-position of the hydroxamate analogue 3. While direct addition of a β-aryl moiety resulted in poor P. falciparum Dxr inhibition, longer linkers between the carbon backbone and the phenyl ring were generally associated with better binding to the enzyme. X-ray structures of the parasite Dxr-inhibitor complexes show that the “longer” compounds generate a substantially different flap structure, in which a key tryptophan residue is displaced, and the aromatic group of the ligand lies between the tryptophan and the hydroxamate’s methyl group. Several analogues emerged as highly potent inhibitors of Plasmodium falciparum in vitro growth. In some cases (e.g. for compounds 7b and 7f) good Dxr inhibitory activity failed to translate in good in vitro activity against the parasite, which may be due to inefficient uptake. Compounds 5a-e likewise failed to inhibit EcDxr and MtbDxr while 6c was optimal for inhibition of these enzymes

Метод проектів у процесі музично-виконавської підготовки майбутнього вчителя музики

(uk) У статті визначається сутність інтегрованого методу художньо-творчих проектів, розкривається його специфіка у процесі музично-виконавської підготовки майбутніх учителів музики.(ru) В статье определяется сущность интегрированного метода художественно-творческих проэктов, раскрывается его специфика в процессе музыкально-исполнительской подготовки будущих учителей музыки

VLT/NACO astrometry of the HR8799 planetary system. L'-band observations of the three outer planets

HR8799 is so far the only directly imaged multiple exoplanet system. The orbital configuration would, if better known, provide valuable insight into the formation and dynamical evolution of wide-orbit planetary systems. We present L'-band observations of the HR8799 system obtained with NACO at VLT, adding to the astrometric monitoring of the planets HR8799b, c and d. We investigate how well the two simple cases of (i) a circular orbit and (ii) a face-on orbit fit the astrometric data for HR8799d over a total time baseline of ~2 years. The results indicate that the orbit of HR8799d is inclined with respect to our line of sight, and suggest that the orbit is slightly eccentric or non-coplanar with the outer planets and debris disk.Comment: 5 pages, 4 figures, 1 table, accepted for publication in A\&A. Updated version includes minor changes made in the proof

Characterization of the Benchmark Binary NLTT 33370

We report the confirmation of the binary nature of the nearby, very low-mass system NLTT 33370 with adaptive optics imaging and present resolved near-infrared photometry and integrated light optical and near-infrared spectroscopy to characterize the system. VLT-NaCo and LBTI-LMIRCam images show significant orbital motion between 2013 February and 2013 April. Optical spectra reveal weak, gravity sensitive alkali lines and strong lithium 6708 Angstrom absorption that indicate the system is younger than field age. VLT-SINFONI near-IR spectra also show weak, gravity sensitive features and spectral morphology that is consistent with other young, very low-mass dwarfs. We combine the constraints from all age diagnostics to estimate a system age of ~30-200 Myr. The 1.2-4.7 micron spectral energy distribution of the components point toward T_eff=3200 +/- 500 K and T_eff=3100 +/- 500 K for NLTT 33370 A and B, respectively. The observed spectra, derived temperatures, and estimated age combine to constrain the component spectral types to the range M6-M8. Evolutionary models predict masses of 113 +/- 8 M_Jup and 106 +/- 7 M_Jup from the estimated luminosities of the components. KPNO-Phoenix spectra allow us to estimate the systemic radial velocity of the binary. The Galactic kinematics of NLTT 33370AB are broadly consistent with other young stars in the Solar neighborhood. However, definitive membership in a young, kinematic group cannot be assigned at this time and further follow-up observations are necessary to fully constrain the system's kinematics. The proximity, age, and late-spectral type of this binary make it very novel and an ideal target for rapid, complete orbit determination. The system is one of only a few model calibration benchmarks at young ages and very low-masses.Comment: 25 pages, 3 tables, 13 figures, accepted for publication in The Astrophysical Journa

Binarity of Transit Host Stars - Implications on Planetary Parameters

Straight-forward derivation of planetary parameters can only be achieved in transiting planetary systems. However, planetary attributes such as radius and mass strongly depend on stellar host parameters. Discovering a transit host star to be multiple leads to a necessary revision of the derived stellar and planetary parameters. Based on our observations of 14 transiting exoplanet hosts, we derive parameters of the individual components of three transit host stars (WASP-2, TrES-2, and TrES-4) which we detected to be binaries. Two of these have not been known to be multiple before. Parameters of the corresponding exoplanets are revised. High-resolution "Lucky Imaging" with AstraLux at the 2.2m Calar Alto telescope provided near diffraction limited images in i' and z' passbands. These results have been combined with existing planetary data in order to recalibrate planetary attributes. Despite the faintness (delta mag ~ 4) of the discovered stellar companions to TrES-2, TrES-4, and WASP-2, light-curve deduced parameters change by up to more than 1sigma. We discuss a possible relation between binary separation and planetary properties, which - if confirmed - could hint at the influence of binarity on the planet formation process.Comment: 9 pages, 3 Figures. Accepted by A&

Heat Treatment Process Energy Efficient Design and Optimisation

AbstractEnergy efficiency optimization ICT (Information and Communication Technology) solutions are currently being developed for energy saving in buildings and, to some ex-tent, also for the manufacturing domain. This paper describes an approach and ICT tool developed for manufacturing process energy efficiency optimization, in particular focused on the heat treatment process of steel casting parts. Traditionally this manufacturing process is designed based on experts experience selecting a predefined temperature-time curve provided customer specifications for the resulting steel parts. However this curve can actually be optimised in terms of energy consumption while keeping required mechanical properties. This improved design is what the tool here described provides, using knowledge based approach for process design and multivariate optimisation and simulation techniques for process optimisation

Lucky Imaging survey for southern M dwarf binaries

While M dwarfs are the most abundant stars in the Milky Way, there is still large uncertainty about their basic physical properties (mass, luminosity, radius, etc.) as well as their formation environment. Precise knowledge of multiplicity characteristics and how they change in this transitional mass region, between Sun-like stars on the one side and very low mass stars and brown dwarfs on the other, provide constraints on low mass star and brown dwarf formation. In the largest M dwarf binary survey to date, we search for companions to active, and thus preferentially young, M dwarfs in the solar neighbourhood. We study their binary/multiple properties, such as the multiplicity frequency and distributions of mass ratio and separation, and identify short period visual binaries, for which orbital parameters and hence dynamical mass estimates can be derived in the near future. The observations are carried out in the SDSS i' and z' band using the Lucky Imaging camera AstraLux Sur at the ESO 3.5 m New Technology Telescope. In the first part of the survey, we observed 124 M dwarfs of integrated spectral types M0-M6 and identified 34 new and 17 previously known companions to 44 stars. We derived relative astrometry and component photometry for these systems. More than half of the binaries have separations smaller than 1 arcsec and would have been missed in a simply seeing-limited survey. Correcting our sample for selection effects yields a multiplicity fraction of 32+/-6% for 108 M dwarfs within 52 pc and with angular separations of 0.1-6.0 arcsec, corresponding to projected separation 3-180 AU at median distance 30 pc. Compared to early-type M dwarfs (M>0.3M_Sun), later type (and hence lower mass) M dwarf binaries appear to have closer separations, and more similar masses.Comment: 18 pages, 9 figures. Minor corrections and changes. Revised to match accepted A&A versio